Separation method and apparatus

Abstract

The invention concerns a method and a device for separation of separable constituents from a liquid medium. The separation device comprises only one cell or a stack of a plurality of adjacent cell, whereby each cell consists of a plate unit containing a filter, an inlet for supplying the liquid medium into a chamber, and outlet for discharging the reject and an outlet for discharging the permeate. The liquid medium is subjected to a strong turbulence created by a convenient designed rotor, possible combined with sound waves, whereby the deposition of separable constituents on the filter is prevented or essentially reduced. According to the invention a rotor is used in which the essentially plane surface of the rotor wings directed toward the filter comprises one or more areas deviating from the plane of said surface; or the surface of the rotor wings directed towards the filter is curved in such a way that the distance between the surface of the wing and the filer is small at the inner portion of the rotor and that said distance gradually increases towards the periphery of the rotor, or the section of the rotor wings in the plane parallel with the filter forms an almost S-shaped surface, whereby the S-shape is continuous.

We claim: 
     
       1. A method for separation of constituents, separable in a filter, from a liquid medium containing such constituents, whereby a separation device is used comprising a cell or a stack of a plurality of adjacent cells, whereby each cell is comprised of: a plate unit containing at least one filter;   at least one inlet for supplying the liquid medium into a chamber;   at least one outlet for discharging part of the liquid medium as reject, whereby said inlet and outlet are positioned on a first side of the filter;   at least one outlet on a second side of the filter for discharging a liquid medium as permeate which has passed through the filter, whereby the liquid medium supplied to the chamber is subjected to a strong turbulence created by a rotor; whereby deposition of separable constituents on the filter is reduced, wherein the rotor comprises a plurality of circumferentially distanced rotor wings in which an essentially plane surface of the rotor wings directed towards the filter comprises one or more areas deviating from the plane of said surface, or   the surface of the rotor wings directed towards the filter is curved in such a way that distance between the surface of the wing and the filter is small at an inner portion of the rotor and that said distance gradually increases towards a periphery of the rotor, or   a section of the rotor wings in a plane parallel with the filter forms an essentially S-shaped surface, whereby the S-shape is continuous.     
     
     
       2. A device for separation of constituents, separable in a filter, from a liquid medium containing such constituents, whereby said device comprises a cell or a stack of a plurality of adjacent cells, whereby each cell is comprised of: a plate unit provided with a through going center hole containing at least one filter;   at least one inlet for supplying the liquid medium into a chamber;   at least one outlet for discharging part of the liquid medium as reject, whereby said inlet and outlet are positioned on a first side of the filter;   at least one outlet on a second side of the filter for discharging a liquid medium as permeate which has passed through the filter, and   a rotor positioned on the first side of the filter, said rotor comprising a plurality of circumferentially distanced rotor wings which are movable along a surface of the filter, whereby the rotor includes a rotor shaft running through the center hole of the plate unit, whereby the rotor wings are designed so that rotational movement of the wings causes strong enough turbulence in surrounding liquid medium to reduce precipitation of separable constituents on the filter, wherein an essentially plane surface of the rotor wings directed towards the filter comprises one or more areas deviating from the plane of said surface, or   the surface of the rotor wings directed towards the filter is curved in such a way that a distance between the surface of the wing and the filter is small at an inner portion of the rotor and that said distance gradually increases towards a periphery of the rotor, or   a section of the rotor wings in a plane parallel with the filter forms an essentially S-shaped surface, whereby the S-shape is continuous.     
     
     
       3. A device according to claim 2, wherein the rotor wings are provided with at least one through hole, at least one recess, at least one boss, or a combination of at least two of said at least one through hole, said at least one recess and said at least one boss. 
     
     
       4. A device according to claim 3, wherein the at least one boss includes bosses composed of separate compressable, liquid or gas impermeable bodies mounted in holes or recesses in the rotor wing or fastened on the surface of the rotor wing. 
     
     
       5. A device according to claim 2, wherein the rotor wings are provided with a least one through hole, at least one recess, at least one boss, or a combination of at least two of said at least one through hole, at least one recess and at least one boss.   
     
     
       6. A device according to claim 5, wherein the surface of the rotor wings directed towards the filter is curved in such a way that the distance between the surface of the wing and the filter is small at an inner portion of the rotor and that said distance gradually increases towards a periphery of the rotor. 
     
     
       7. A device according to claim 6, wherein the at least one boss includes bosses composed of separate compressable, liquid or gas impermeable bodies mounted in holes or recesses in the rotor wing or fastened on the surface of the rotor wing. 
     
     
       8. A device according to claim 2, wherein the S-shaped rotor possesses a convex profile formed so that an angle α between a line L drawn from the rotor shaft to an arbitrary point P on the profile and a tangent T to the profile in said point, is essentially constant. 
     
     
       9. A device according to claim 2, further including a sound wave transmitter and/or a device for obtaining an electric field.